1. Field of the Invention
The present invention pertains to an apparatus for enhancing the patency of a patient's upper airway, and, in particular, an apparatus for stabilizing anatomical features associated with the upper airway so as to minimize airway obstruction or restriction. The invention further pertains to an intraoral apparatus having selectively adjustable moving members for optimally positioning various anatomical features associated with the upper airway for optimal upper airway stability, and to a system using such intraoral apparatus, alone or in combination with positive airway pressure or ventilation, as a therapeutic treatment for upper airway instability.
2. Description of the Related Art
Although upper airway stabilization can be used in a wide range of medical applications, the following description discusses the invention as a treatment for obstructive sleep apnea, hypopnea, and upper airway resistance syndrome. Obstructive sleep apnea or OSA, obstructive sleep hypopnea, and upper airway resistance syndrome (UARS) are among a variety of known disorders characterized by episodes of complete or partial upper airway obstruction during a state of diminished consciousness, such as sleep, anesthetization, or post anesthesia. OSA, hypopnea, and UARS cause intermittent interruption of ventilation during sleep with the consequence of potentially severe oxyhemoglobin desaturation. Typically, those afflicted with OSA, hypopnea, and UARS experience repeated, frequent arousal from sleep in response to the oxygen deprivation. The arousals result in sleep fragmentation and poor sleep continuity.
Consequences of OSA, hypopnea, and UARS may include debilitating daytime sleepiness and cognitive dysfunction, systemic hypertension, cardiac dysrythmias, pulmonary artery hypertension and congestive heart failure. Other consequences may include a predisposition to myocardial infarction, angina pectoris, stroke, right ventricular dysfunction with cor pulmonale, carbon dioxide retention during wakefulness as well as during sleep, and continuous, reduced arterial oxygen tension. Moreover, the cognitive impairment resulting from OSA, hypopnea, and UARS puts those afflicted at elevated risk of accidents.
The pathogenesis of the airway obstruction that characterizes OSA, hypopnea, and UARS can include both anatomic and functional abnormalities of the upper airway that result in increased air flow resistance. Such abnormalities may include narrowing of the upper airway due to suction forces created during inspiration, the effect of gravity pulling the tongue back to appose the pharyngeal wall, and insufficient muscle tone in the upper airway dilator muscles, among others. It is also believed that excessive soft tissue in the anterior and lateral neck, as commonly observed in obese persons, can apply sufficient pressure to internal structures to narrow the upper airway and restrict air flow.
Conventional treatment of OSA, hypopnea, and UARS has included surgical intervention, such as uvalopalotopharyngoplasty, gastric surgery for obesity, mandibular advancement procedures, maxillo-facial reconstruction, and tracheostomy. However, surgery potentially involves considerable risk of post-operative morbidity and mortality. In addition, the failure rate of surgery is disturbingly high. Pharmacological therapy has also been proposed to treat OSA, hypopnea, and UARS; however, results have been generally disappointing.
More recently, continuous positive airway pressure (CPAP) or bi-level positive airway pressure applied during sleep has been used to treat OSA, hypopnea, and UARS patients. Positive pressure is applied in the upper airway to splint or support the airway, thereby preventing its collapse and the resultant airway obstruction. Although positive airway pressure can nearly always stabilize the upper airway, in some cases the required pressure magnitude is unacceptable for other reasons. For example, positive airway pressure may adversely affect spontaneous patient respiration, or may not be well tolerated by the patient.
The prior art is also replete with disclosures of intraorally fitted appliances, including U.S. Pat. Nos. 4,981,437 and 4,932,867, that disclose a method and apparatus for constructing dentures, which are useful, for example, in treating breathing disorders. U.S. Pat. No. 4,386,405 discloses a device for measuring the location, attitude, or change of location of a patient's lower jaw. U.S. Pat. No. 4,859,181 relates to optical measurement of jaw movement. U.S. Pat. Nos. 3,998,209 and 4,220,142 disclose conditioning systems for use in a program of behavior modification to eliminate snoring, while U.S. Pat. No. 4,976,618 relates to treatment of temporomandibular joint dysfunction and bruxism. U.S. Pat. No. 3,297,021 discloses an intraoral strain gauge and telemetering of information from an intraoral location to an outside indicator.
U.S. Pat. No. 5,018,533 purports to disclose a process for reducing the occurrence of apneic episodes for persons with no teeth. U.S. Pat. No. 4,901,737 purports to disclose apparatus and method for repositioning the mandible in an inferior or open, and anterior or protrusive position as compared to the normal closed position of the jaw. In general, lower jaw or mandible positioning devices are known, although not necessarily for OSA, hypopnea, and UARS treatment.
The following U.S. patents purport to relate to tongue positioning and/or retaining apparatus: U.S. Pat. Nos. 5,154,184, 5,092,346, 5,046,512, 4,676,240, 4,169,473, 4,304,227 and 4,593,686. Other patents addressing the matter of tongue positioning include the following: U.S. Pat. Nos. 5,649,540, 5,465,734, 5,373,859, 5,052,409, 4,715,368, 4,196,724, 3,884,226, 3,312,216 and 3,132,647, as well as European patent 0182387 and British patent 874,480. The following patents purport to relate to chin straps or similar apparatus intended to hold the jaw closed: U.S. Pat. Nos. 3,312,217, 2,711,730 and 1,990,411.
Still other patents relate to apparatus for interaction with the soft palate in the user's oral cavity. These include U.S. Pat. No. 4,669,459 and 5,316,020, German patent no. DE 40 26 602 and European patent no. EP 0264516. Other patents of general interest include U.S. Pat. No. 5,056,534 and 2,705,006, German patent nos. 65194 and 2320501, and PCT publication no. WO 92/05752 and European patent application no. 0 487 469 A1.
While the above-identified conventional devices and techniques are purported to treat upper airway instability, such as OSA or snoring, they are successful, if at all, in only a limited pool of patients or under limited circumstances. Therefore, there remains a relatively large number of patients who's airway disorder is believed to be treatable using an intraoral appliance, yet conventional appliances are ineffective, overly burdensome, uncomfortable, or any combination thereof.